Electric switch



' (No Madam 2 sheets-sheen 1. J. B. SMTH 8a A. L. C-LOUGH.

ELEGTRIQ SWITCH.

Patented Nov. 5,1895.

Ul b @a (No Mode1.\ 2 Sheets-Sheet 2.

J. B. SMITH & A. L. GLOUGH. ELECTRIC SWITCH.

NC. 549.162. Patented Nv. 5,1895.

UNITED STATES `PATENT OFFICE.

JOSEPH BRODIE SMITH AND ALBERT L. CLOUGH, OF MANCHESTER, NEW

HAMPSHIRE.

ELECTRIC SWITCH.

SPECIFICATION forming part of Letters Patent N o. 549,162, datedNovember 5, 1895.

Application flledApril 26, 1895. Serial No. 547,207. (No model.)

To @ZZ whom it may concern:

Be it known that we, JOSEPH BRODIE SMITH and ALBERT L. OLOUGH, citizensof the United States, and residents of Manchester, in the county ofHillsborough and State of New Hampshire, have invented new and usefulImprovements in Electric Switches, of which the following, taken inconnection with the accompanying drawings, is a specification.

This invention relates to improvements in means for protecting electricmotors from damage by careless handling or otherwise, as from thethrowing onto the motor of an excessive load or the throwing onto themotor of the full electrical pressure when the motor is in a state ofrest, the functions of the device being to disconnect the motor from thesupply-circuit in case the current which the machine is taking becomesdangerous and capable of over heating the machine and burning out theinsulation, and also to disconnect it from the circuit in case of thecessation or failure of the line-circuit.

This our present invention is an improvement on the patent granted toJoseph Brodie Smith for electric switch April 17, 1894, No. 518,471, andit is carried out as follows, reference being had to the accompanyingdrawings, wherein- Figure 1 represents a front elevation and partialsection of the invention, showing a j ackknife-switch of the double-polevariety having line-wires connected to its terminals. Fig. 2 representsa central longitudinal section on the line 2 2 shown in Fig. 1. Fig. 3represents a longitudinal section on the line 3 3 shown in Fig. 1. Fig.4 represents a cross-section on the line 4 4 shown in Fig. 1. Fig. 5represents an enlarged detail section of the detent and releasing-leverfor the pivoted armature; and Fig. 6 represents an enlarged detaillongitudinal section of the electromagnet-core and its adjustablepole-piece. Fig. 7 represents a diagrammatic view of the switchconnections.

Similar letters refer to similar parts wherever they occur on thedifferent parts of the drawings. Y

In the drawings, A represents a base of insulating material adapted tobe secured to a wall or other convenient object.

B and C are the metal switch-levers, pivoted, respectively, at B/ C onthe plate A, and having their free ends connected to an insulatedcross-bar D, provided with a hard rubber or other suitable handle (Z, ina manner like that shown and described in the above-mentioned patent.

To the levers B and C are secured, respectively, the metal switch platesor blades B C, and below the latter are secured to the base A the forkedmetal contact-pieces B3, B4, O3, and C4, like that shown and describedin the Smith patent aforesaid.

E and F represent the line-wires connected, respectively, to the cups orbinder-posts e'and f, which are metallically connected, respectively,with the contact-pieces B3 and U3, as shown.

g is a cup or binder-post metallically connected to the contact-pieceC4.

h and t' represent cups or binder-posts secured to the plate A andconnected by wires to the electric motor O, as follows: O 0" are thefield-coils of said motor, on which P and P are the pole-pieces, P therotary armature, and p the commutator, as usual in devices of this kind.Q is the rheostat or resistanceboX used in starting the electric motor,as usual. R and R3 are the brushes having their free ends bearingagainst the commutator, as is common in electric motors. From the cup gleads a wire R to the field-coil O'l and armature-commutator p. From thecup h leads the wire R to the iield-coil O', the wire of which isconnected to the wire of the coil O by means of the wire 1', as shown inFig. 1.

In Fig. 1, S is a wire leading from the binder-post 1', through therheostat O3, to the commutator on the armature P, as shown. K K aresprings designed to hold the switch normally in an open position, so asto cause the circuit from the line to the motor to be interrupted. L andL are spring-contacts carried on the switch-arms B C and having theirfree ends tipped with carbon rods Z, which when the switch is in aclosed position touch similar carbon rods or blocks Z l', secured to thecontacts B4 C". Said spring-contacts are designed to receive the sparkwhich is made upon the breaking of the circuit, and are s0 IOOconstructed as to hold the circuit closed until the metallic contacts ofthe switch have parted.

The controlling mechanism of the switch which constitutes the novel partof the arrangement, is fully shown in Figs. l, 2, and 5, and consists ofa spring-pressed detent M, which is slotted, as shown in Figs. 2 and 5,and pivoted at d to a projection or bracket D on the switch-bar D. Thisdetent is arranged to engage with a catch n, forming part of aspringpressed releasing-lever N, which is pivoted at n to theelectromaonct frame or standard` Q, as shown in Figs. l, 2, and' 5. Tothe Q3, of which Q is the upper one, Q the middle one, and the lowerone, as shown in Fig. 2. To the middle one Q is pivoted at t the rockingarmature T, having at its upper position a notch t, capable of engagingwith the free end of the releasing-lever N, which is the continuation ofthe catch n previously mentioned. The slotted detent M is acted upon bya suitable spring m, (shown in Figs. 2 and 5,) which tends to push ittoward the catch n, and in addition to such longitudinal yielding motionto and from the catch n it is also capable of rotation on the pivot d,as shown. Upon the upper leg Q of the electromagnet is placed a spoolq', around which is Wound a coil of wire U, which is in series with thefield-current of the motor by means of wires h b, leading, respectively,to the cup h and contactepiece B4. Upon the lower leg Q3 of theelectromagnet is placed a spool Q3, around which is wound a coil of wireU', which is traversed by the armature-current of the motor by means ofwires i' and b, leading, respectively, to the cup z' and contact-pieceB4, as shown. The armature T is thus under the attraction of both coilsU and U', which act in contrary directions on said armature, whichconstitutes a diierential electromagnetic device.

In practice the coil U is made of somewhat coarser wire than the coil U,as shown in Fig. 2.

In detail in Fig. 6 is shown a means for adjusting the core Q to andfrom the armature T for the purpose of changing the pull which the coilU exercises on the said armature, and it consists of an adjustablescrew-threaded sleeve or pole-piece q, which is adjustably screwed onthe forward end of said core Q and capable of adjustment to and from thearmature for the purpose stated. The lower core Q3 may likewise beprovided with such adjustable pole-piece, if so desired.

lt will be seen that when the releasing-lc ver N is engaged with thenotch t in the armature T the catch n on said lever is placed in such aposition that the detent M engages with it, thus holding the switch.closed. In case, however, the releasing-lever N leaves the notch t it ispushed upward by the action of the springs K K against the torce of asmall spring n, (shown in Fig. 1,) which normally tends to return saidlever N to its lowest position for interlocking with the notchedarmature. the lever N from the armature the catch n retreats from thedetent M, the latter frees itself, and the switch opens.

In Fig. l, X represents a spring-pressed button attached to a metal rodX, adapted to slide in a perforation in the block h, and adapted to bebrought in contact with the block t', so as to metallically connect saidblocks for the purpose of short-circuiting thc winding, which is inseries with the motoriield, thus allowing the switch to open in the samemanner as through the failure of the current.

In Fig. 1, y is a small spring bearing against the inside of the pivotedarmature T, above its fulcrum t, for the purpose of disengaging the hookt from the releasing-lever N during the opening of the switch.

The action and operation of the switch are as follows \Vhen it isclosed, the circuit is completed and the currents flow in both spools Uand U', according to the connections shown. Owing to the preponderanceof the magnetic force of the upper coil U in circuit with the field ofthe motor, the notch t on the arma- Iture T is brought into engagementwith the releasingelever N and the switch is held closed. In case,however, that the current passing in the motor becomes abnormally large,its attraction overcomes the attraction due to the field-current, andthe said notch disengages from the releasing-lever N, which allows theswitch to open, as previously stated. In case, also, that theline-current fails from any reason, the small spring shown at y actswith sufficient force to disengage the arma* ture notch. t from thereleasing-lever N and the switch opens. In case it is desired to adjustthe switch to open on a smaller armature-current, it is only necessaryto screw the movable pole-piece Q farther onto its core Q, thusdecreasing the attraction due to the iield current and relativelyincreasing the attraction due to the armature-current. In order toeffect the opposite result, the pole piece q is moved in the oppositedirection.

By the use of the releasing mechanism here shown it is possible tocontrol a switch that is actuated by strong opening-springs withoutnecessitating too strong electromagncts, or to waste too much electricalenergy.

Having thus fully described the nature, construction, and operation. ofour invention, we wish to secure by Letters Patent and claim-d ln anautomatic electric switch, the combination with a switch of springstending` to hold said switch in an open position, of an electro-magneticmechanism consisting of two electro-magnets having their windingsrespectively in series with the armature and field oi' an electricmotor, said electro-mag- During such release oi'v IOO IIO

nets acting in mechanical opposition upon a pivoted armature and one orboth of them having a movable pole piece capable of :tdjustment in sucha manner as to Vary the distance between the cores of said magnets andtheir armature; the said armature being adapted for engagement with thelong arm of zt pivoted angular lever, said lever carrying on its shortarm a catch capable of engagement with a detent fastened to said switchand When so en gaged acting to hold the switch

